Temperature Extraction Scheme for Composite Insulator Core Rod Sheath of Overhead Transmission Lines Based on Oriented Bounding Boxes

ABSTRACT Unmanned Aerial Vehicle (UAV) inspection of overhead transmission line composite insulators allows for the rapid acquisition of large amounts of infrared images of insulators in service, which can be used to analyse their operational status. However, efficiently and accurately analysing these images remains a challenge. This paper proposes a temperature extraction scheme based on Oriented Bounding Boxes (OBB) detection results for the intelligent extraction of the core rod sheath temperature of composite insulators on overhead lines. First, a You Only Look Once version 11 (YOLOv11) model is established to detect OBB for composite insulators in the infrared images, achieving a mAP50:95 of 91.5%. Based on the detection results, an insulation central axis localisation scheme that integrates candidate lines and skeleton extraction is proposed, which accurately locates the central axis of the composite insulator in the image. Finally, using filtering and extremum extraction methods, the temperature points along the central axis of the core rod are accurately extracted. The proposed temperature extraction scheme reduces the probability of abnormal temperature occurrences in the test set to 4.9%, nearly matching the effect of manual temperature extraction. This provides an effective framework for the intelligent processing of infrared inspection images of overhead line composite insulators.